1. Field of the Invention
The present invention relates to a starter motor with an intermediate gear wheel used for a vehicle. More particularly, it relates to a moving means to cause the movement of the intermediate gear wheel when an overrunning clutch is moved.
2. Discussion of Background
FIG. 6 is a longitudinal cross-sectional view partly broken of a conventional starter motor with an intermediate gear wheel. In FIG. 6, reference numeral 1 designates a d.c. motor in which a rotary shaft 3 projects forwardly (to the right side in drawing) from an armature 2. Numeral 4 designates the yoke of the d.c. motor, on which field magnetic poles 5 are mounted. Numeral 6 designates a front bracket attached to the yoke 4, which supports the front end portion of the rotary shaft 3 by means of a sleeve bearing 7.
Numeral 9 designates an overrunning clutch mounted on the rotary shaft 3 so as to be slidable in the axial direction. The overrunning clutch 9 is constructed as follows. A clutch outer 10 is fitted to the outer circumference of the rotary shaft by means of a helical spline 8 so as to transmit a torque of the rotary shaft 3. A clutch inner 11 is supported by the rotary shaft 3 through a sleeve bearing 19 so that a one-way revolutional force is transmitted to the clutch outer 10 through a roller 12. A pinion 13 is formed integrally with the front end portion of the clutch inner 11. Numeral 14 designates a clutch cover fixed to the clutch outer 10 together with a plate 15 by means of caulking. Numeral 16 designates a stop ring attached to the clutch outer 10 to form a fitting groove between a step portion formed in the clutch outer and the stop ring. Numeral 18 designates an eccentricity control ring firmly attached to the inner circumferential portion of the clutch outer 10.
Numeral 20 designates a shift lever having a pivotal point which is supported by the inner wall of the front bracket 6 and a bearing plate 21, the lower end portion extending downwardly from the pivotal point being engaged with the fitting groove 17 to move the overrunning clutch 9 in the axial direction. The upper end portion of the shift lever 20 is engaged with the front end of the plunger (not shown) of an electromagnetic switch which is located at the upper portion of the motor. The shift lever is turnable around the pivotal point. The bearing plate 21 is received on a grommet 22 attached to the yoke 4 through a shock absorbing spring 23. Numeral 29 designates a stopper fixed to the rotary shaft 3.
Numeral 24 designates an intermediate shaft fixed to the front bracket 6 in parallel to the rotary shaft 3, numeral 25 designates a grommet fitted to a hole formed in the front bracket 6 to receive the intermediate shaft 24, and numeral 26 designates an intermediate gear wheel mounted on the intermediate shaft 24 through a sleeve bearing 28 fixed to the inner circumferential portion of the intermediate gear wheel 26 so as to be rotatable and slidable in the axial direction. Numeral 30 designates a movable connecting member made of a strengthened synthetic resin or metal having a resistance to bearing and a large mechanical strength. The movable connecting member comprises a boss portion 30a which is loosely fitted to the outer circumference of an extended boss portion 26a projecting from the intermediate gear wheel 26. A snap ring 31 is provided on the extended boss portion 26a of the intermediate gear wheel to prevent the movable connecting member 30 from coming-off. A circular-arc-shaped fitting portion 30b is formed integrally with the upper portion of the rear end of the boss portion 30a and the fitting portion 30b is inserted in the lower half portion of the fitting groove 17 of the overrunning clutch so as to move together in the axial direction.
FIG. 7 is a perspective view showing the movable connecting member 30 comprising the boss portion 30a and the circular-arc-shaped fitting portion 30b formed integrally with the lower end of the boss portion 30a.
The operation of the conventional starter motor will be described.
When a current is supplied to an exciting coil (not shown) of the electromagnetic switch, the plunger is attracted to turn the shift lever 20 in a counter-clockwise direction in FIG. 6. Accordingly, the overrunning clutch 9 is moved forwardly (in the direction of A) until the overrunning clutch 9 hits the stopper 29 attached to the rotary shaft 3. When the overrunning clutch 10 is moved forwardly, the intermediate gear wheel 26 is also moved forwardly through the movable connecting member 30 to be interlocked with the ring gear 35 of the internal combustion engine of the vehicle. Then, a fixed contact of the electromagnetic switch is closed to feed a current in the circuit of the d.c. motor to thereby activate the armature 2. The revolution of the rotary shaft 3 is transmitted to the intermediate gear wheel 26, hence the ring gear 35 via the overrunning clutch 9 and the pinion 13, whereby the internal combustion engine is started.
In the conventional starter motor with an intermediate gear wheel, when the intermediate gear wheel 26 is moved in association with the overrunning clutch 9, a force is applied to the stop ring 16. When the interlocking of the intermediate gear wheel 26 with the ring gear 35 is performed in a normal state, a force to be applied to the stop ring 16 is small. However, in an abnormal operation such that during idling revolution of the intermediate gear wheel 26, it is brought into interlocking with the ring gear 35 by inserting the key switch of the automobile, a large moving force is resulted in the direction of A in the overrunning clutch 9 because of the helical spline 8 although the movement of the intermediate gear wheel 26 is stopped when the gear wheel is brought to contact with the end surface of ring gear 35, and the circular-arc-fitting portion 30b of the movable connecting member 30 fitted to the intermediate gear wheel 26 impinges the stop ring 16. The impingement may causes the deformation or breakage of the stop ring 16.